1. Field of the Invention
This invention is in the fields of tree breeding and molecular biology, and pulp and paper properties evaluations. This invention allows for an enhanced efficiency of selection for superior trees in both plantation and natural populations, based on fiber length.
2. Description of the Prior Art
Many tree characteristics of commercial importance, such as wood density, volume growth and fiber properties, are known to exhibit continuous levels of variation in both natural and plantation populations [J. E. Eckenwalder. xe2x80x9cSystematics and Evolution of Populusxe2x80x9d in Biology of Populus (Stettler, R. F., Bradshaw, H. D., Heilman, P. E., and Hinckley, T. M. eds) NRC Research Council Press, Ottawa ON, pp. 7-32 (1996)]. The greatest barrier to progress in selection for quantitative traits is the lack of repeatability of phenotypic traits in different environments. Hence, identifying individuals with the most favorable genotype is one of the most difficult and challenging aspects of tree breeding. The roots of quantitative trait variation lie in the fact that such traits are controlled by not one but several genetic components working together. Despite this complexity, advancing technology in genetic marker development has made it possible to identify the genetic regions which contribute to the control of continuously variable properties. These regions are known as quantitative trait loci or QTL""s [E. S. Lander and D. Botstein, Genetics 121, 185-199 (1989)]. A genetic marker is any qualitatively inherited phenotype that can be used to monitor the segregation of alleles that are genetically linked to the marker. It is possible to identify and monitor genetic markers that are closely linked to QTLs. In order for a QTL to be identified or mapped to a specific chromosomal location, it must first be demonstrated that the quantitative trait of interest is highly correlated with a genetic marker.
In this fashion, QTLs have been mapped for a number of traits including volume growth, wood density and bud flush date. To this point, however, no properties which directly impinge upon the pulp and paper industry have yet been QTL mapped.
Breeding and selection for enhanced wood and fiber properties in trees has historically been necessarily complex. Traditional approaches to tree improvement suffer from a number of problems. Firstly, the intervals between generations are necessarily longxe2x80x94even fast-growing species (e.g., poplar) must be left for 4-8 years to develop. Secondly, the ability to select trees on the basis of only one or two physical characteristics is limited given the large amount of genetic material involved in crosses and the consequent complexity of the genetic intermixing which occurs.
Similarly, in natural forests, superior trees for industrial use cannot be readily identified without undertaking extensive characterization studies. This invention will help circumvent some of the necessary testing and facilitate the selection of superior tree lines.
One aim of the present invention is to provide means to circumvent some of the necessary testing and facilitate the selection of superior tree lines.
In accordance with another embodiment of the present invention, there is provided a method of identifying a genetic marker associated with a genetic locus conferring at least one enhanced property selected from the group consisting of fiber length, coarseness, DBH (diameter at breast height), density and yield in a family of trees, which comprises the steps of:
a) obtaining a sexually mature parent tree exhibiting enhanced fiber length properties;
b) obtaining a plurality of progeny trees of the parent tree by performing self or cross-pollination;
c) assessing multiple progeny trees for each of a plurality of genetic markers;
d) identifying genetic markers segregating in an essentially Mendelian ratio and showing linkage with at least some other of the plurality of genetic markers;
e) measuring fiber length in multiple progeny trees; and
f) correlating the presence of at least one enhanced property with a least one marker identified in step d) as segregating in an essentially Mendelian ratio and showing linkage with at least some of the other markers, the correlation of the presence of at least one enhanced property with a marker indicating that the marker is associated with a genetic locus conferring an enhanced property; wherein the family of trees comprises a parent tree and its progeny.
In accordance with another embodiment of the present invention there is provided a method of producing a plurality of clonal trees that have at least one enhanced property selected from the group consisting of fiber length, coarseness, DBH, density and yield, which comprises the steps of:
a) obtaining a sexually mature parent tree exhibiting enhanced fiber length properties;
b) obtaining a plurality of progeny trees of the parent tree by performing self or cross-pollination;
c) assessing multiple progeny tress for each of a plurality of genetic markers;
d) identifying genetic markers segregating in an essentially Mendelian ratio and showing linkage with at least some other of the plurality of genetic markers;
e) measuring fiber length in multiple progeny trees;
f) correlating the presence of at least one enhanced property with a least one marker identified in step d) as segregating in an essentially Mendelian ratio and showing linkage with at least some of the other markers;
g) selecting a progeny tree containing a marker identified in step f) as associated with a genetic locus conferring at least one enhanced property; and
h) vegetatively propagating the progeny tree selected in step g) to produce a plurality of clonal trees, essentially all of the clonal trees exhibiting at least one enhanced property.
In accordance with another embodiment of the present invention there is provided a method of producing a family of trees wherein at least about half exhibit at least one enhanced property selected from the group consisting of fiber length, coarseness, DBH, density and yield, which comprises the steps of:
a) obtaining a sexually mature parent tree exhibiting enhanced fiber length properties;
b) obtaining a plurality of progeny trees of the parent tree by performing self or cross-pollination;
c) assessing multiple progeny tress for each of a plurality of genetic markers;
d) identifying genetic markers segregating in an essentially Mendelian ratio and showing linkage with at least some other of the plurality of genetic markers;
e) measuring fiber length in multiple progeny trees;
f) correlating the presence of at least one enhanced property with a least one marker identified in step d) as segregating in an essentially Mendelian ratio and showing linkage with at least some of the other markers;
g) selecting a progeny tree containing a marker identified in step f) as associated with a genetic locus conferring at least one enhanced property; and
h) sexually propagating the progeny tree selected in step g) to produce a family of trees, at least about half of the family of trees containing a genetic locus conferring at least one enhanced property and the family of trees exhibiting the at least one enhanced property.
In accordance with one embodiment of the present invention, the method may further comprise constructing a genomic map of the parent tree using the plurality of genetic markers.
The genetic marker loci may be restriction fragment length polymorphism (RFLPs) or random amplified polymorphic DNA (RAPDs) which may in turn be correlated with quantitative traits loci (QTLs).
The parent tree may be the seed parent tree to each of the progeny trees, and leaf or cambium tissue from the progeny trees is assessed for the presence or absence of genetic markers in step c).
The parent tree may be of the genus Populus, more specifically of a species of Populus trichocarpa, Populus deltoides, Populus tremuloides or a hybrid thereof.
In accordance with one embodiment of the present invention, there is provided a genetic map of QTLs of trees of the genus Populus associated with fiber length as set forth in FIG. 8.
In accordance with one embodiment of the present invention, there is provided a genetic marker of fiber length of trees, which comprises a 800 bp amplification product, wherein presence of the product in an amplified DNA sample from the trees is indicative of a short fiber length xe2x89xa60.92 mm and absence of the product is indicative of long fiber length  greater than 0.92 mm.
For the purpose of the present invention the following terms are defined below.
The term xe2x80x9cDBHxe2x80x9d is intended to mean diameter (cm) of the tree stem at breast heightxcx9c1.3 m.
The term xe2x80x9ccoarsenessxe2x80x9d is intended to mean a weight to length ratio for fibers (mg/m).
The term xe2x80x9cyieldxe2x80x9d is intended to mean the amount of fiber recovered from a given weight of wood (%).
The term xe2x80x9cdensityxe2x80x9d is intended to mean a weight to volume ratio for wood (g/cm3).
The expression xe2x80x9cenhanced fiber length propertiesxe2x80x9d is intended to mean a fiber greater than 0.92 mm in length.
The expression xe2x80x9cshort fiber lengthxe2x80x9d is intended to mean fibers xe2x89xa60.92 mm.
The expression xe2x80x9clong fiber lengthxe2x80x9d is intended to mean fibers  greater than 0.92 mm.
The expression xe2x80x9c800 bp amplification productxe2x80x9d is intended to mean an amplification product, such as a PCR product, of the RAPD marker G03 of size 800 base pairs.